The regulation of interstitial fluid volume in the small bowel is governed by the interaction of transcapillary, lymphatic and transmucosal volume flows and forces. The interplay of these volume flows and forces is of utmost importance in assuring the prompt removal of absorbed nutrients and volume in the absorptive state yet limits excess accumulation of interstitial fluid due to capillary filtration in the nonabsorptive state. The overall objective of the studies outlined in this proposal is to more fully characterize the forces, membrane parameters, and flows which govern interstitial fluid volume regulation in the small bowel under various pathological (chronic portal hypertension, acute anaphylactic reaction to food antigen) and physiological (fat absorption) conditions. Particular attention is given to studying the effect of the aforementioned conditions on a) capillary and interstitial forces and lymph flow, b) capillary permeability to macromolecules, and c) physicochemical properties of the interstitium (e.g., macromolecule exclusion). From the information obtained in these studies we can build a comprehensive model of interstitial fluid volume regulation in the small bowel. Furthermore, the proposed studies should improve our understanding of the factors responsible for the interstitial edema associated with various intestinal disorders.